Add Bitbucket microagent and backend implementation (#9021)

Co-authored-by: openhands <openhands@all-hands.dev>
Co-authored-by: Engel Nyst <enyst@users.noreply.github.com>
Co-authored-by: Rohit Malhotra <rohitvinodmalhotra@gmail.com>

openhands/resolver/interfaces/issue.py

@@ -121,5 +121,5 @@ class IssueHandlerInterface(ABC):
     def get_converted_issues(
         self, issue_numbers: list[int] | None = None, comment_id: int | None = None
     ) -> list[Issue]:
-        """Download issues from Gitlab."""
+        """Download issues from the git provider (GitHub, GitLab, or Bitbucket)."""
         pass